A Long Island inventor says he will sue the FDNY for “blatantly” copying a concept for a rescue rope system he gave the department three years ago.

Patrick O’Kane, of Merrick, a former Port Authority employee who painted the George Washington Bridge and the antenna on the World Trade Center, said he designed the bailout system called the LifeCender – a fireproof rope that feeds into a plastic lowering device clipped to a firefighter’s waist harness – after 9/11.

He said he will file a lawsuit claiming the FDNY infringed on 13 patents he has on the LifeCender.

“I worked alongside firefighters at Ground Zero and kept thinking something should be done to allow these guys to get out of buildings quickly,” he said. “So I developed the LifeCender in the hopes I could save a firefighter’s life.”

The system, which would allow a firefighter to jump from a high-rise building and automatically descend slowly to the ground, was offered to the department in November 2001 and immediately tested, according to O’Kane.

He said the LifeCender went through six variations and three years of testing at the FDNY’s Fort Totten research and development facility in Queens, but was eventually declined in favor of a rope system the FDNY introduced on Oct. 4.

Although the two devices are different – the FDNY’s device has a hook and a lever mechanism to control descent while O’Kane’s has no anchor and is activated and controlled by body weight – O’Kane said the concept is identical.

“Their device completely copies my concept,” he said. “I was the first one to bring them a slow-descent, hands-free escape device. That was three years ago . . . Now all of a sudden, two firefighters die and they develop the same thing to save face? C’mon. It’s blatant.”

He added the FDNY system looks exactly like his backup system, which uses almost identical hardware. “They stole the concept, then used my backup system to implement it,” he said. “And really my backup system isn’t safe enough to give to firefighters. If you don’t know what you’re doing, you can descend too fast and really hurt yourself.”

FDNY spokesman Frank Gribbon called the accusations “totally ridiculous,” saying the department’s system was developed in-house. Petzl, a French manufacturer, said it designed the chosen gadget from FDNY specs.

“The LifeCender was one product we tested, and it didn’t make it out of the second round,” he said, adding the department was concerned LifeCender’s weight-controlled descent would be too slow in an emergency.

“In an emergency situation, a firefighter needs to control how fast he gets out of the building,” Gribbon said. “He can’t be hanging there waiting for the thing to get going.”